Method and apparatus for measuring oil in water

ABSTRACT

Method and apparatus for measuring minute quantities of oil in water in which an annular oil collecting chamber having a transparent cover with graduated volume indicia is secured at the upper ends of coaxial output tubes extending upwardly from the narrow upper end of a frusto-conical centrifugal separation chamber, so that the separated oil flows from said separation chamber through the annular space between said output tubes into said collecting chamber, where its volume may be determined with reference to said volume indicia.

ilnited States Patent [1 1 Jenkins Nov. 13, 1973 METHOD AND APPARATUS FOR MEASURING OIL IN WATER [75] Inventor: Ralph E. Jenkins, Irving, Tex.

[73] Assignee: Core Laboratories, Inc., Dallas, Tex.

[22] Filed: Jan. 6, 1972 [21] AppL No.: 215,814

[52] US. Cl 73/61.1 R, 233/1 B [51] Int. Cl. G0ln 11/00, GOln 33/18 [58] Field of Search 73/61.1 R, 61 R, 73/61.4, 53; 233/1 B, 26, 27; 356/70, 208

[56] References Cited UNITED STATES PATENTS 2,485,209 10/1949 Lundal .7 2331/27 2,885,145 5/1959 Danielsson et al 233/26 3,168,473 2/1965 Goda et a1. 73/6l.4 X

Primary ExaminerRichard C. Queisser Assistant Examiner-Joseph W. Roskos Att0rney-William C. Conner [57] ABSTRACT Method and apparatus for measuring minute quantities of oil in water in which an annular oil collecting chamber having a transparent cover with graduated volume indicia is secured at the upper ends of coaxial output tubes extending upwardly from the narrow upper end of a frusto-conical centrifugal separation chamber, so that the separated oil flows from said separation chamber through the annular space between said output tubes into said collecting chamber, where its volume may be determined with reference to said volume indicia.

6 Claims, 2 Drawing Figures METHOD AND APPARATUS FOR MEASURING OIL IN WATER The present invention relates to a method and apparatus for measuring minute quantities of oil in water.

Such a method and apparatus are meeded, for example, in determining compliance with governmental regulations limiting the oil content of brine produced from offshore or tidal oil wells and dumped in the ocean.

Regulations of The United States Geological Survey currently in force prevent the dumping of brine having an average oil content greater than 50 parts per million. Such regulations, of course, create a need in the oil production industry for an accurate, reliable and rapid method and a practical and inexpensive apparatus for measuring oil in water at concentrations of less than 50 parts per million.

The present invention satisfies this need by providing a relatively simple but practical and accurate oilmeasuring attachment which may readily be attached to a liquid-liquid centrifugal separator of a conventional, commercially available type.

In the drawings:

FIG. 1 is a diagrammatic vertical sectional view of a typical liquid-liquid centrifugal separator which has been modified by the addition of an illustrative oilmeasuring attachment in accordance with the present invention.

FIG. 2 is an enlarged fragmentary vertical sectional view of the oil-measuring attachment shown in FIG. 1.

The typical centrifugal separator shown in FIG. 1 includes a sample bowl for receiving the liquid mixture to be separated, a feed pipe 10a extending axially downward from the bottom of the bowl 10 for gravity feeding of the liquid downwardly into a feed cup 12 which communicates with the wide lower end of a generally frusto-conical separation chamber 14. Within the separation chamber 14 are a stack of vertically spaced, frusto-conical discs 16 having circumferentially spaced, aligned vertical distribution holes 18 herein, the discs 16 being supported between upper and lower funnels 20 and 22 whose narrow upper ends are formed to provide integral, concentric output tubes 20a and 22a, respectively, which extend upwardly in coaxial relation to the separation chamber 14. The narrow upper end of the separation chamber 14 extends upwardly to form a third output tube 14a which encircles the output tubes 20a and 22a in concentric relation therewith, and which is provided at its upper end with a sealing flange 14b which extends inwardly into liquid-tight engagement with the tube 20a. Spaced around the periphery of the outermost tube 14b near its upper end are a series of regulating screws 24 having axial bores through which liquid may flow, under centrifugal force, outwardly into an annular collecting cover 26 which surrounds the tube 14b at the level of the regulating screws and which is formed at one side to provide an integral, downwardly inclined tangentially extending output spout 26a.

The separation chamber 14 and the output tubes 14a, 20a and 22a are all rotatable in unison at high speed by a drive mechanism (not shown).

This conventional separator mechanism is modified by the addition of the collecting chamber generally designated 28. As best shown in FIG. 2, the collecting chamber 28 is formed by an annular base member 30 whose inner edge is internally threaded for threaded engagement with an externally threaded surface at the upper end of the middle output tube 200. At its outer edge the base member 30 is provided with an upwardly extending circular flange 300 having an internal, upwardly facing shoulder 30b which supports the outer edge portion of an annular, transparent cover member 32.

The cover member 32 is held down by a pair of retaining rings 34 and 36, the inner retaining ring 34 being internally threaded for threaded engagement with an externally threaded surface at the upper end of the inner output tube 22a, and the outer retaining ring 36 being internally threaded for threaded engagement with an externally threaded surface at the upper end of the flange 30a. The outer edge of the cover member 32 is compressively engaged by an O-ring 38 which is partially recessed in a groove in the inner face of the flange 30a just above the shoulder 30b, thereby forming a liquid-tight seal between the outer edge of the cover member 32 and the base member 30.

The interior of the collecting chamber 28 thus communicates with the annular space between the output tubes 20a and 22a. The interior of the collecting chamber 28 is preferably exponentially tapered in depth toward its outer periphery by upward inclination of the upper surface of the base member 30. The transparent cover member 32 is provided with volume indicia 40 which are graduated inwardly from the periphery of the collecting chamber, the exponential tapering of the depth of the collecting chamber 28 preferably being such that the ratio between the increments of radius and the increments of volume is uniform across the width of the chamber. Thus, indicia 40 representing equal units of volume maybe equally spaced radially. To facilitate reading of the volume indicia while the mechanism is rotating, the indicia are preferably either concentric circles extending completely around the cover member 32 or a series of markings spaced circumferentially around the cover member at coincident radial positions to give the visual effect of continuous circles when the cover member is rotating at high speed.

The operation of the apparatus is as follows:

With the separation chamber 14 and the associated parts rotating at high speed, a sample of the water to be tested for oil content is placed in the sample bowl 10 and is gravity fed through the feed pipe 10a and the cup 12 into the lower end of the separation chamber 14. The hydrostatic pressure of the sample liquid forces it upwardly through the distribution holes and between the discs 16.

The high-speed rotation of the separation chamber 14 causes the heavier liquid phases (in the case, the water) to be centrifugally forced along the underside of the discs 16 to the outer portion of the chamber, while the lighter phases (in this case, the oil) are displaced inwardly along the upper side'of the discs 16 to the inner portion of the chamber. The water is displaced upwardly along the outer wall of the chamber into the annular space between the two outer tubes 14a and 20a, from which it passes through the regulating screws 24 into the collecting cover 26 and down spout 26a. The oil is displaced upwardly along the inner wall of the chamber through the annular space between the two inner tubes 20a and 22a and into the collecting chamber 28, where centrifugal force causes it to be distributed to a uniform depth around the periphery of the chamber. While the apparatus is still rotating, the volume of the accumulated oil may be determined by reference to the volume indicia 40.

A number of batches of sample liquid may be processed through the apparatus while it is still rotating, with the oil from each batch being accumulated in the collecting chamber 28 to the point where the chamber is filled. Alternatively, the sample bowl may be replaced by an input pipe which extends into the feed cup 12 to force feed the water mixture continually into the rotating separator mechanism at a known rate, with the operation continuing as long as desired, to the point where the collecting chamber is filled. In either case, by dividing the measured volume of accumulated oil by the known throughput volume of the water, the concentration of oil in water may be readily determined. The exponential tapering of the thickness of the collecting chamber 28 also facilitates the measurement of small volumes of oil at the periphery of the chamber.

The retaining rings 34 and 36 may readily be unthreaded from the tubes 22a and a respectively and the cover member 32 removed to permit easy cleaning of the collecting chamber 28 preparatory for the next test.

I claim:

1. A method of measuring minute quantities of oil in water comprising providing a centrifugal separator of the type having a frusto-conical separation chamber with a central input duct communicating with its wide lower end and a pair of coaxial output tubes at the narrow upper end of said separation chamber, wherein the annular space between said output tubes communicates with the upper end of said separation chamber, with an annular oil collecting chamber having an annular base member secured to the upper end portion of the outer one of said output tubes, and a transparent annular cover member having its inner edge surrounding the inner one of said output tubes, and its outer edge sealed to the outer edge of said base member in liquid-tight manner, and graduated volume indicia on said cover member, feeding a measured volume of said water through said input duct into the lower end of said separation chamber, rotating said separation chamber at high speed to cause separation of said oil, removing said oil from the upper end of said separation chamber through said annular space into said collecting chamber, and determining the volume of the separated oil accumulated in said collecting chamber by reference to said volume indicia.

2. A method as described in claim 1 in which said volume indicia are graduated inwardly from the periphery of said collecting chamber and in which the volume of said oil is determined while said apparatus is rotating at high speed.

3. A measuring attachment for a centrifugal separator of the type having a frusto-conical separation chamber with a pair of concentric output tubes extending coaxially upward from the narrow upper end of said separation chamber, with the annular space between said output tubes communicating with the interior of the narrow upper end of said separation chamber to re ceive the separated lighter phase liquid, said attachment comprising a collecting chamber formed by an annular base member secured to the upper end portion of the outer one of said output tubes, and a transparent annular cover member having its inner edge surround ing the inner one of said output tubes, and its outer edge sealed to the outer edge of said base member in liquid-tight manner, and graduated volume indicia on said cover member.

4. Apparatus as described in claim 3 in which said collecting chamber is tapered in depth, being thinner at its periphery than at its inner portion.

5. Apparatus as described in claim 4 the taper is exponential.

6. Apparatus as described in claim 3 in which the inner edge of said base member is internally threaded for engagement with external threads on said outer tube, and in which said cover member is removably secured on top of said base member by an inner retaining ring threaded onto said inner tube and an outer retaining ring threaded on said base member. 

1. A method of measuring minute quantities of oil in water comprising providing a centrifugal separator of the type having a frusto-conical separation chamber with a central input duct communicating with its wide lower end and a pair of coaxial output tubes at the narrow upper end of said separation chamber, wherein the annular space between said output tubes communicates with the upper end of said separation chamber, with an annular oil collecting chamber having an annular base member secured to the upper end portion of the outer one of said output tubes, and a transparent annular cover member having its inner edge surrounding the inner one of said output tubes, and its outer edge sealed to the outer edge of said base member in liquid-tight manner, and graduated volume indicia on said cover member, feeding a measured volume of said water through said input duct into the lower end of said separation chamber, rotating said separation chamber at high speed to cause separation of said oil, removing said oil from the upper end of said separation chamber through said annular space into said collecting chamber, and determining the volume of the separated oil accumulated in said collecting chamber by reference to said volume indicia.
 2. A method as described in claim 1 in which said volume indicia are graduated inwardly from the periphery of said collecting chamber and in which the volume of said oil is determined while said apparatus is rotating at high speed.
 3. A measuring attachment for a centrifugal separator of the type having a frusto-conical separation chamber with a pair of concentric output tubes extending coaxially upward from the narrow upper end of said separation chamber, with the annular space between said output tubes communicating with the interior of the narrow upper end of said separation chamber to receive the separated lighter phase liquid, said attachment comprising a collecting chamber formed by an annular base member secured to the upper end portion of the outer one of said output tubes, and a transparent annular cover member having its inner edge surrounding the inner one of said output tubes, and its outer edge sealed to the outer edge of said base member in liquid-tight manner, and graduated volume indicia on said cover member.
 4. Apparatus as described in claim 3 in which said collecting chamber is tapered in depth, being thinner at its periphery than at its inner portion.
 5. Apparatus as described in claim 4 the taper is exponential.
 6. Apparatus as described in claim 3 in which the inner edge of said base member is internally threaded for engagement with external threads on said outer tube, and in which said cover member is removably secured on top of said base member by an inner retaining ring threaded onto said inner tube and an outer retaining ring threaded on said Base member. 